NANOPARTICLES WITH PBS CORE OF 12 NM AND SHELL OF APPROXIMATELY 3 NM WERE SYNTHESIZED AT PBS:ZNS RATIOS OF 1.01:0.1 USING MERCA PTOPROPIONIC ACID AS STABILIZING AGENT. PBS/ZNS NANOPARTICLES PRESENT A DRAMATICALLY INCREASE OF PHOTOLUMINESCENCE INTENSITY, CONFIRMING THE CONFINEMENT OF THE PBS CORE BY INCREASING THE QUANTUM YIELD FROM 0.63 TO 0.92 BY THE ADDITION OF THE ZNS SHELL.IN THIS CASE, THE SYNTHESIS BY MICROWAVE METHOD ALLOWS OBTAINING NANOPARTICLES WITH ENHANCED OPTICAL CHARACTERISTICS THAN THOSE OF NANOPARTICLES SYNTHESIZED BY COLLOIDAL METHOD.

RECENTLY, MUCH INTEREST WAS AROUSED IN SYNTHESIS OF SEMICONDUCTING NANOPARTICLES INTENDED FOR APPLICATION IN MODERN MICROELECTRONIC DEVICES. THE POSSIBILITY OF PRODUCING SEMICONDUCTING NANOPARTICLES WITH CONTROLLABLE SIZE AND SHAPE IS BEING EXTENSIVELY STUDIED.PBS HAS BEEN WIDELY USED IN MANY FIELDS SUCH AS PB+2 ION SELECTIVE SENSOR, IR DETECTORS, SOLAR ABSORBER AND PHOTOGRAPHY [1]. PBS@SIO2 CORE-SHELL NANOPARTICLES WERE SUCCESSFULLY SYNTHESIZED BY THE SIMPLE WET CHEMICAL METHOD. THE SYNTHESIZED PRODUCT HAS BEEN CHARACTERIZED BY POWDER X-RAY DIFFRACTION (XRD), UV–VIS SPECTROPHOTOMETRY, FTIR SPECTROSCOPY, SCANNING ELECTRON MICROSCOPY (SEM), TRANSMISSION ELECTRON MICROSCOPY (TEM), ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDX). THE CRYSTALLINITY OF THE SIO2 SPHERES, PBS/SIO2 CORE–SHELL NANOSTRUCTURES WERE STUDIED BY XRD.

IN THE LAST FEW DECADES, NANOSTRUCTURED SEMICONDUCTING MATERIALS HAVE ATTRACTED SIGNIFICANT ATTENTION IN SCIENCE AND TECHNOLOGY BECAUSE OF THEIR OUTSTANDING OPTICAL AND ELECTRICAL PROPERTIES AND EXTENSIVELY POTENTIAL APPLICATIONS IN DIFFERENT AREAS, INCLUDING MICROELECTRONICS, ELECTROOPTICS, PHOTOCATALYSIS, PHOTOELECTROCHEMISTRY, ENERGY CONVERSION AND BIOLOGICAL IMAGING [1, 2].AMONG THE SEMICONDUCTING MATERIAL, PBS IS A WELL-KNOWN P–P SEMICONDUCTOR WITH CUBIC CRYSTAL STRUCTURE AND NARROW BANDGAP (0.41 EV AT 300 K). LEAD SULFIDE HAVING A LARGE EXCITON BOHR RADIUS (18 NM) SHOWS STRONG QUANTUM-SIZE EFFECTS IN NANOCRYSTALLINE FORM AND HAS BEEN WIDELY USED IN OPTOELECTRONIC DEVICES [3, 4].IN THIS WORK, WE HAVE SUCCESSFULLYREPORTED A SIMPLE, CLEAN, CHEAP AND TEMPLATE-FREE SYNTHESIS ROUTE OF WELL-DEFINED PBS NANOSTRUCTURES VIA NEW PRECIPITATION METHOD USING PB (CH3COO) 2.3H2O AS A PRECURSOR AND THIOUREA AS A SULFUR SOURCE UNDER ALKALINE MEDIA. THIS EXPERIMENTS WERE PERFORMED IN TWO DIFFERENT TEMPERATURES (ROOM TEMPERATURE AND 70OC) AND IN THE PRESENCE OF SURFACTANT ORSURFACTANT-FREE CONDITIONS. THE STRUCTURE AND MORPHOLOGY OF AS-PREPARED PBS NANOSTRUCTURES WERECHARACTERIZED BY X-RAY DIFFRACTION (XRD), FIELD EMISSION SCANNING ELECTRON MICROSCOPY (FESEM) AND PHOTOLUMINESCENCE SPECTROSCOPY.

QUANTUM DOTS (QDS) ARE TINY PARTICLES OF SEMI-CONDUCTORS THAT ARE EASY AND CHEAP TO PRODUCE AND CAN BE USED IN SOLAR CELLS TO CONDUCT THE ELECTRONS [1]. QUANTUM DOTS ARE NOT ONLY COST-EFFECTIVE, BUT ARE ALSO VERSATILE, HIGHLY-EFFICIENT IN CONDUCTING AN ELECTRICAL CURRENT, AND ARE AN ETHICAL OPTION FOR THE NEXT GENERATION OF SOLAR CELLS.IN RECENT YEARS, INORGANIC SEMICONDUCTOR NANOCRYSTALS (ALSO KNOWN AS QUANTUM DOTS, QDS) HAVE BEEN FOUND TO BE PROMISING FOR NEXT GENERATION SOLAR CELL [2-3]. LEAD CHALCOGENIDES (PBS, PBSE AND PBTE) AND THEIR ALLOYS HAVEBEEN THE SUBJECT OF CONSIDERABLE RESEARCH DUE TO THE TECHNOLOGICALIMPORTANCE OF THESE MATERIALS, IN CRYSTALLINE AND POLYCRYSTALLINEFORMS. LEAD CHALCOGENIDES HAVE MUCH IN COMMON IN THEIR PHYSICOCHEMICAL PROPERTIES: THEY ARE ISOMORPHOUS, HAVE THE SAME TYPEOF CHEMICAL BONDING, CAN BE PREPARED BY SIMILAR METHODS, HAVESIMILAR PHASE DIAGRAMS, AND CAN BE DOPED IN A SIMILAR MANNER. FOR NON-WATER-SOLUBLE COLLOIDAL PBS QDS, THE HOT-INJECTION APPROACH REPORTED BY HINES AND SCHOLES [4] SEEMS TO BE THE BEST TO ENGINEER HIGH-QUALITY QD ENSEMBLES. THIS HOT-INJECTION METHOD WAS CONDUCTED BY HEATING A MIXTURE OF LEAD OXIDE (PBO) AND OLEIC ACID (OA, AS CAPPING LIGANDS) IN OCTADECENE (ODE) AT 100OC UNDER AR FOR ONE HOUR FOLLOWED BY THE INJECTION OF A SOLUTION OF (TMS)2S AT 90OC. AFTER THE HOT INJECTION, THE GROWTH WAS KEPT EITHER AT 80OC OR ROOM TEMPERATURE. THE PRODUCTS WERE CENTRIFUGED AND THE MIXTURE OF PBS NANOCRYSTALS AND UNREACTED LEAD OLEATE WERE COLLECTED.